Its a personal choice. Certainly a capture card will suffice for recording un-coded video.
HDTV tuner can function as HDTV tuner and video capture card. My HDTV tuner have video inputs that can record directly from SAT BOX/CABLE BOX.
It's true that an HDTV tuner can record directly from the Sat/Cable source, and you were correct in mentioning the word "un-coded" in your response. But I wonder if most who read this understand what that really means.
HDCP - the copy protection scheme employed in Sat/Cable TV converters - may well prevent you from recording a lot of channels you thought you'd be able to record just by connecting the converter to your video/tuner card. No one is going to record a premium channel like HBO. HDCP simply won't allow it under any circumstances. Some HD channels, like National Geographic, are also blocked on my cable system, while others, like The Discovery Channel, can be recorded as long as they are sent through the Sat/Cable converter box.
I record a lot of things broadcast on TV. Typically, I record the pgm onto the DVR which I then re-record on to a DVD using my external DVD player/burner. I then bring those files from the DVD into my computer where I am able to edit out the commercials and create the final program I can now record to a permanent DVD. This is a cumbersome process which I'd like to streamline by recording directly into my computer. I don't think I'll be able to do this without adding a seperate converter box to a compter tuner card, an expense I'm not willing to pay. Nor will a tuner card connected directly to the cable TV coax line (without the converter box) allow me to bring in any channels above the first 125 channels.
I realize this response my go a bit further than the OP's question, but I just wanted people to know that just hooking up the cable TV coax line to an HDTV turner card does not mean HD channels are going to flow into one's computer.